To determine the central atom of which compound has four bond pairs and two lone pairs, we will analyze each option step by step.
### Step 1: Analyze Option 1 - SF4
1. **Identify the central atom**: In SF4, the central atom is Sulfur (S).
2. **Count valence electrons**: Sulfur has 6 valence electrons, and each Fluorine (F) has 7 valence electrons. Thus, the total number of valence electrons is:
- Sulfur: 6
- 4 Fluorines: 4 × 7 = 28
- Total = 6 + 28 = 34 valence electrons.
3. **Draw the Lewis structure**: Connect the 4 Fluorine atoms to Sulfur with single bonds. This uses 8 electrons (4 bonds).
4. **Distribute remaining electrons**: After forming bonds, 26 electrons remain. Each Fluorine needs 6 more electrons to complete their octet (24 electrons total), leaving 2 electrons.
5. **Count bond pairs and lone pairs**:
- Bond pairs: 4 (from the S-F bonds)
- Lone pairs: 1 (the 2 remaining electrons form 1 lone pair)
6. **Conclusion**: SF4 has 4 bond pairs and 1 lone pair. **Not the answer.**
### Step 2: Analyze Option 2 - XeF4
1. **Identify the central atom**: In XeF4, the central atom is Xenon (Xe).
2. **Count valence electrons**: Xenon has 8 valence electrons, and each Fluorine has 7 valence electrons. Thus, the total number of valence electrons is:
- Xenon: 8
- 4 Fluorines: 4 × 7 = 28
- Total = 8 + 28 = 36 valence electrons.
3. **Draw the Lewis structure**: Connect the 4 Fluorine atoms to Xenon with single bonds. This uses 8 electrons (4 bonds).
4. **Distribute remaining electrons**: After forming bonds, 28 electrons remain. Each Fluorine needs 6 more electrons to complete their octet (24 electrons total), leaving 4 electrons.
5. **Count bond pairs and lone pairs**:
- Bond pairs: 4 (from the Xe-F bonds)
- Lone pairs: 2 (the 4 remaining electrons form 2 lone pairs)
6. **Conclusion**: XeF4 has 4 bond pairs and 2 lone pairs. **This is the answer.**
### Step 3: Analyze Option 3 - NH4+
1. **Identify the central atom**: In NH4+, the central atom is Nitrogen (N).
2. **Count valence electrons**: Nitrogen has 5 valence electrons, and each Hydrogen has 1 valence electron. Thus, the total number of valence electrons is:
- Nitrogen: 5
- 4 Hydrogens: 4 × 1 = 4
- Total = 5 + 4 = 9 valence electrons (but we subtract 1 for the positive charge).
3. **Draw the Lewis structure**: Connect the 4 Hydrogen atoms to Nitrogen with single bonds. This uses 4 electrons (4 bonds).
4. **Distribute remaining electrons**: After forming bonds, 5 electrons remain.
5. **Count bond pairs and lone pairs**:
- Bond pairs: 4 (from the N-H bonds)
- Lone pairs: 0 (no remaining electrons)
6. **Conclusion**: NH4+ has 4 bond pairs and 0 lone pairs. **Not the answer.**
### Step 4: Analyze Option 4 - SF6
1. **Identify the central atom**: In SF6, the central atom is Sulfur (S).
2. **Count valence electrons**: Sulfur has 6 valence electrons, and each Fluorine has 7 valence electrons. Thus, the total number of valence electrons is:
- Sulfur: 6
- 6 Fluorines: 6 × 7 = 42
- Total = 6 + 42 = 48 valence electrons.
3. **Draw the Lewis structure**: Connect the 6 Fluorine atoms to Sulfur with single bonds. This uses 12 electrons (6 bonds).
4. **Distribute remaining electrons**: After forming bonds, 36 electrons remain. Each Fluorine needs 6 more electrons to complete their octet (36 electrons total), leaving 0 electrons.
5. **Count bond pairs and lone pairs**:
- Bond pairs: 6 (from the S-F bonds)
- Lone pairs: 0 (no remaining electrons)
6. **Conclusion**: SF6 has 6 bond pairs and 0 lone pairs. **Not the answer.**
### Final Answer
The compound with a central atom that has 4 bond pairs and 2 lone pairs is **XeF4** (Option 2).
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